24 



Regulation of Size in Unicellular Organisms 



24 hours, the length had reached only sixty percent. 

 Either the conditions were not proper for growth, or 

 growth in breadth occurred as well as growth in 

 length. 







4 8 12 16 20 



Time after fission in hours 



24 



Figure 10. Growth in length in Paramecium caudatum at 15.3° to 18.7° C. 

 Forty-four living individuals were measured at three-hour intervals, and 

 the percentage lengths were averaged. (Data of Schmalhausen and Synga- 

 jewskaja, '25). 



Mizuno {'27) measured not only length and breadth 

 but also shadow-area of fixed individuals of Parame- 

 cium caudatum. His data are equally extensive with 

 those of Jennings, but the results shown in figure 11 

 are different in several important respects. In pass- 

 ing, it may be noted that the product of length and 



